China's new cryogenic trick can reduce 99% of microchip defects

Chinese researchers from Peking University, Tsinghua University, and the University of Hong Kong have developed a novel cryo-electron tomography (cryo-ET) technique to dramatically reduce defects in microchip manufacturing, specifically during the photolithography process. Photolithography involves using light to pattern circuits on silicon wafers coated with a photoresist, but microscopic particles formed during the chemical development stage often cause defects that ruin chips, especially at cutting-edge 5-nanometer or smaller nodes. Previously, manufacturers could not observe the behavior of the photoresist developer liquid in detail, making defect causes difficult to pinpoint. By rapidly freezing the developer liquid at –175°C mid-process and using electron tomography to create 3D molecular-level images, the team discovered that photoresist polymers form tangled clumps through weak hydrophobic interactions, creating 30–40 nm particles. About 70% of these molecules fail to dissolve properly and accumulate at the air-liquid interface, later redepositing on